viirya commented on a change in pull request #24557: [SPARK-27653][SQL] Add max_by() and min_by() SQL aggregate functions URL: https://github.com/apache/spark/pull/24557#discussion_r283238524
########## File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/MaxByAndMinBy.scala ########## @@ -0,0 +1,127 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.spark.sql.catalyst.expressions.aggregate + +import org.apache.spark.sql.catalyst.analysis.TypeCheckResult +import org.apache.spark.sql.catalyst.dsl.expressions._ +import org.apache.spark.sql.catalyst.expressions._ +import org.apache.spark.sql.catalyst.util.TypeUtils +import org.apache.spark.sql.types._ + +/** + * The shared abstract superclass for `MaxBy` and `MinBy` SQL aggregate functions. + */ +abstract class MaxMinBy extends DeclarativeAggregate { + + def valueExpr: Expression + def orderingExpr: Expression + + protected def funcName: String + // The predicate compares two ordering values. + protected def predicate(oldExpr: Expression, newExpr: Expression): Expression + // The arithmetic expression returns greatest/least value of all parameters. + // Used to pick up updated ordering value. + protected def orderingUpdater(oldExpr: Expression, newExpr: Expression): Expression + + override def children: Seq[Expression] = valueExpr :: orderingExpr :: Nil + + override def nullable: Boolean = true + + // Return data type. + override def dataType: DataType = valueExpr.dataType + + override def checkInputDataTypes(): TypeCheckResult = + TypeUtils.checkForOrderingExpr(orderingExpr.dataType, s"function $funcName") + + // The attributes used to keep extremum (max or min) and associated aggregated values. Review comment: Good for me. +1 ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
